Electron-emitting cathode and the process of manufacturing the same.



A. McL. NICOLSON & E. C. HULL.

ELECTRON EMITTING CATHODE AND THE PROCESS OF MANUFACTURING THE SAME.

APPLICATlON FILED mo. 26. 19:4.

LQGQfiM. Patented Dec. 19,1916.

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ALEXANDER MOLEAN NICOLSON, OF NEW YORK, N. Y., AND EMERSON CHURCH HULL,

OE MONTCLAIB, NEW JERSEY, ASSIGNOBS, BY MESNE ASSIGNMENTS '1'0 WESTERN;

ELECTRIC COMPANY, INCOBEQBATED, A. CORPQB'ATION 01 NEW YORK.

memoir-Emma carnonnann rm. raocnss or manuracrumc rnn same.

' 1,209,324. cific i n or wa m n Patented net. as, rare.

Application filed December as, 1914. semi-menses.

To all whom it may concern: g S itable for use as an electron-emitting Be it known that we, Annxannnn MCLEANI cathode when treated in accordance with the 55 .NICOLSON, a subjectaof the Kirl g of Great process'of this invention, and Fig. 2 illus- Britain, and Emerson Cmmcrr FULL, a cititrates the use of such a filamentin a'thermi- -5 zen of the United States, residingat New onic repeater of the audion type.

York, in the county of New York and State The 1nvention,both as a recess and as a y of New York and at Montclair, in the county product, will now be more ully set forth in cc of Essex and State of New Jersey, ,respecconnection with a detailed description of the tively, have invented certainnew and useful preferred method of practising the process. Improvements -in Electron- Emitting Cath- Y A twisted platinumribbon or filament 2 odes and the Process of Manufacturing the having, for example, awidth of three-tenths Same, of which the following is a full, clear, of a millimeter and a thickness of five-hum ta -concise,'and exact dcscriptio dredths of a millimeter, is preferably used This invention relates toelectron-emitting as the heating element. The filament is ;l5 cathodes, such as areused in .audions or thoroughly cleansed in some suit ble mana vacuum tube and to the process of manuner, as, for example,'by dipping it for a few 7 facturing suc cathodes. Its object is to minutes in chromic or in nitric acid, and provide electronrcmittin cathodes, having then Washing it first in water and then in-a greatly increased durabi 'ty and constancy strong solution of ammonia. The filament .20 of activity. is then extended'between the opposite eleca A recognized defect of oxid-coated electrodes of a source of electric current. In tron-emitting cathodes has been that, though order to ascertain that there are no defects having an initially high activity, they soon in the filament, it may be .incandesced by deteriorate in use, becoming less and less passing an electric current through the fila- 26 active.' In accordance with this invention, it ment. 1f the filament is found to be satisis possible to produce cathodes having such factory, as evidenced by uniformity of indesirably high activity and also having a candescencait is thencoated with alternatett' uniformity 0 action over a very long period. coatings of'strontium hydroxid and barium ofuse. jnssmate. One feature of th process consists in' ap- Ihe strontium hvdroxid may be prepared plying to a plati or other suitable elec-' ass stifl' paste and, in such case, is d luted trical conductor, which becomes the heating with water before being applied to the fila- S5" element of the cathode, a coating consisting ment.'-'The diluted strontium hydroxid is V of an organic compound of ametal of the applied to the filament in any suitable man-' 86'- alkaline earth group, and thenraising said ner, as for example by moving atroufigih con-. coating to the ignition temperature. Thev tainingthe fiui lengthwise of the ament processprefer-aha "l includes the coating of while the latter dips mto the fluid in the M the electrical con ctor with successive coat- "trou h. 'During this stage of theprocess,

. ings containing a metal of the alkaline earth the lament is slightly heated, ,as for ex- 40' group, preferably a coating or coatings of "ample by a current of 1.4 amperes, that is to strontlum hydroxid alternating with a coata temperature of, .for -'example, 100 C. ing or coatings-of barium resinate, the latter Such heating facilitates the operation of being the preferred aforementioned organic coating and causes a uniform coating to be compound of a metal of the alkaline earth deposited on the filament. Several of such 45 group. The final product resulting from coatings are preferably applied in succes-' the practice of the rocess is an,electrode sion, and in practice it has been found that having a dense and c osely adherent coating four of such successive layers orcoatings of great'durability and constancy of activity give the most satisfactory result. After each. when the electrode is used as an electron- -coating, or less often if preferred, the lila- 50 emitting cathode. ment is raised for a few seconds to an incan- In theaccompanying drawing Figure 1 descing temperature, thus hardening the represents in'enlarged form a portion of a coating on the filament. The filament is filamentary conductor which has been found next coated with. barium resinate, such oranic compound of barium having ound to be most suitable'for obtalmng a smooth, adherent and active coating. In order that the resinate may be readily applied as a coating, it is heated to a temperature that will make the resinate sufficiently fluid for that purpose. In practice, the filament has been heated electrically to a temperature of approximately 600? 0., and a' trough containing the barium reslnate moved lengthwise of the filament, the latterdipfimg into the resinate and the resinate being ,ept sufiiciently fluid by the heated filament.

J5 may be applied in succession, preferably the same number as the aforementioned coatings of strontium hydroxid. .And, as before, after each coating or. after two or more sue cessive coatings, the filament is raised for a few secondatoan incandescing temperature.

The process, of alternately applying a coating or coatings of strontium ydroxid and a coating or coatings of barium resmate ma be kept up until a sufliciently heavy 25. mo tiple'coating covers the filament orv other f form of electrode that is under treatment.

In practice,

cessive coatings of strontium hydroxid, then four successive coatings of barium resinate ,then four'additional successive coatings of strontium hydroxid, and finally four additional successive coatin of barium resinate give a satisfactory res'u t;

coating is com- When the operation of 85 pleted the filament is electrically heated to mcandescence for the-purpose of raising the barium resinate coatin to an ignition temperature, as for examp e, to a temperature of approximately 800 to 900 C; The 40 coating is maintained at such high temperature for some time, for example, for about two hours.

As a'result-of the aforementioned treatment the filament is covered with a dense,

closely-adherent film, which is believed to consist ofbarium oxid and strontium oxid.

' Saidfilm is of exceedingly great durability andiconstancy of electron-emittin activity when the filament is, used as .tl e heated cathode of a vacuum tube.- v

What is claimed is:

1. The recess of manufacturing an elecplying to an electrical conductor. a coating.

- containing a metal of the alkaline .earth' grou .bakin said coa'tingwthen' a l anotl idr- 'coatgig containing .anothe m dt?aq of the alkaline (group; and subse- ,quently sub ectmg sald'coating's to prolonged .60 high temperature.

'2. The process of manufacturingan elec "tron-emittm cathode,- which consists in coating arr-e ectrical conductor with an oxidof a metal of the alkaline earth group then 35 apply ng anothercoating consisting of an A taming a metal of the alkaline earth group;

number of such coatings of barium resinate v to a in h temperature.

it has been found that four suc- 1 droxl of strontium; then ap of a metal of the alkalineearth group, and .sub ecting said coating to an ignition temorganic compound ofa metal of the alkaline earth group; and subsequently subjecting said coatings to a prolonged high temperature.

3. The process of manufacturing an electron-emittin cathode, which consists in coatin an e ectrical conductor with the hydroxi of a metal of the alkaline earth group; heating said conductor and thereby converting. the hydroxid coating into an oxid coating; then applying another coatin'g consisting of an organic'compound con and subsequently subjecting said coatings 4. T e rocess of manufacturing an electron-emittm cathode, which consists in coating an e ectrical conductor with a coating comprising a fluid medium and an osid of a metal ofthe' alkaline earth group; drying said coating; then applying a "coating consisting of an organic com ound of a metal; and subsequently s'ub ecti ng said coatin to aprolonged hi h temperature.

5. he process of manu acturing an electron-emittm .cathode, which consists in coatin an e ectrical conductor with the hyly'gg a coating of barium resinate; and r a y subjecting' said coatings to a high temperature. 5 6. The process of manufacturing 'an else-- tron-emittin cathode, which consists in, coatingean e ectrical conductor with an orearth group, and subjecting said coating'to an ignition temperature.

7. The rocess of manufacturing an electron-emittm cathode, which consists in- 'coatin ene ectrical" conductor with-the resinate o a metal of the alkaline earth group,

and subjecting said coating to an ignition temperature. I 8.. The process of manufacturing an electron-emittm cathode, which consists in coating platinum with an organic compound 1 1 9 perature. v 9. The process of manufacturing an electron-emittmg cathode, which consists in coating platinum with ,barium resinate, and subjecting said u coating to an ignition temtren-emittmg cathode, winch consists in ap- "prolonged ignition ,temperature by passing .'an electric current through said filament.

lL-"Theprocess of manufacturing an electron-emittin cathode, which consists in "coating platinum with alternate coatings of strontium hydroxid and barium resinate,

and then subjecting said to e ee. m

naoaeaa electric current through saidplatinum 12. The process of manufacturing an electron-emitting cathode which consists in slightly heating a conducting filament and passing it whi e heated throu h a coating compound containing a metal 0 the alkaline earth group, and then raising the temperature of the coated filament. v

13. An electron-emitting cathode comprising an electrode having a multiple coating consisting of superposed coatings of the oxids of difierent metals of the alkaline earth group.

v14. An electron-emitting cathode comprising an electrode having a multiple coating consisting of a coating containing ba- 1 rium and a coating contalnmg strontium.

15; An electron-emitting cathode comprising an electrode having a multiple coating consistin of alternate coatings of barium oxid an strontium oxid. v

16. An electron-emitting cathode comprising a platinum electrode having a multiple coating consistingpf superposed coatings containing different metals of the alkaline earth group.

17. An electron-emitting cathode comprising a platinum electrode having a multiple coating consisting of alternate coatof barium oxid and strontium oxid.

, witness whereof we hereunto'subscribe our names this 23rd ay of December A. D.,- 1914. r v

ALEXANDER MOLEAN NICOLSON. I'lllillltSOll CHURCH HULL. Witxiesscigs;

n a a. 1 31a 

